Field Devices Vortex Manual
40 Issue 7 December 2009
FIELD DEVICES
5 TECHNICAL INFORMATION: FIELD DEVICES
5.1 General
This chapter contains detailed technical information on the use of field devices (detectors and audible
and visible alarms) with Vortex. You may need to refer to this during installation, configuration or
maintenance of the Vortex system.
If you simply use Vortex for monitoring and responding to alarms, it is not necessary to read this
chapter. See chapter 6, Operation.
5.2 Gas Detectors
5.2.1 Gas detector location
There are no rules that dictate the siting and location of detectors. However, considerable guidance is
available from:
• BS EN 50073:1999, Guide for Selection, Use and Maintenance of Apparatus for the Detection
and Measurement of Combustible Gases or Oxygen.
Similar codes of practice of other countries may be used where applicable. In addition, certain
regulatory bodies publish specifications giving minimum gas detection requirements for specific
applications.
The detector should be mounted where the gas is most likely to be present. The following points
should be noted when locating gas detectors:
• To detect gases that are lighter than air, for example, methane, detectors should be mounted at
high level. Crowcon recommends the use of a Collector Cone.
• To detect gases that are heavier than air, for example, butane, detectors should be mounted at low
level. Contact Crowcon for details.
• To detect gases with similar weight to air, for example, hydrogen sulphide, mount the detector at
normal breathing height.
• Mounting of oxygen detectors requires knowledge of the gas displacing the oxygen. For example,
carbon dioxide is heavier than air and displaces oxygen at a low height. Under these
circumstances oxygen detectors should be placed near ground level.
• When locating detectors, consider the possible damage caused by natural events such as rain or
flooding. For detectors mounted outdoors, Crowcon recommends the use of weatherproof caps or
spray deflectors.
• Consider ease of access for functional testing and servicing.
• Consider how the escaping gas may behave due to natural or forced air currents. Mount detectors
in ventilation ducts if appropriate.
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